Under disease pressure, what is the typical outcome over generations if some individuals are immune?

Under disease pressure, what is the typical outcome over generations if some individuals are immune?

• A. Immune individuals survive and increase population immunity over generations.
• B. Non-immune individuals dominate.
• C. No change occurs in immunity levels.
• D. The disease is eradicated instantly with no effect on selection.

Answer: (A)

Under disease pressure, traits that help survival become more common because those individuals leave more offspring. If some individuals are immune, they survive the outbreak and reproduce, passing on the immunity trait to their children. Over generations, the frequency of immune individuals increases, boosting overall population immunity. Non-immune individuals have lower survival and reproductive success under the disease, so their numbers decline relative to the immune group. The result is a gradual rise in immunity within the population rather than an instant eradication or no change at all.

Under disease pressure, traits that help survival become more common because those individuals leave more offspring. If some individuals are immune, they survive the outbreak and reproduce, passing on the immunity trait to their children. Over generations, the frequency of immune individuals increases, boosting overall population immunity. Non-immune individuals have lower survival and reproductive success under the disease, so their numbers decline relative to the immune group. The result is a gradual rise in immunity within the population rather than an instant eradication or no change at all.